Metal sounding board for pianos



Dec. 21 1926.

- F. FRANKEL METAL SOUNDING BOARD FOR PIANOS Filed Sept. 25, 1922 FFHDOLF FRANKEL r with the lastlnentioned embodiment by pro FREDOLF TEA METAL Application filed September 25,

In my cepending application Serial No. 368,230 I have described a metal soundin board for pianos the edge portions of wh are contracted or shortened relatively to the portions within said edges whereby the sounding-board obtains a certain cup-sna iae or convexity, and there is simultaneously oroduced a stress or tension in the board which in turn produces an. increased resounding power. According to one QiDlDOlllh ment the sounding-board is provided with corrugations or bent-up folds 0r ribs having approximately V-shaped cross section and projecting above the front side of the sounding-board, each of said rios bei together its ends at the ed soundingboard for the purpose of producing contractions of the edge poi-thins of the sounding-board.

I have now found that it is possible to obtain an increased bearing power or spring;

and thus also a still more increased resoiu ing; power as well as greater sensitiveness of a soundingboard constructed in accordance viding on the face of the board opposite c that from which the corrugations or ribs project, ribs or laths, for instance of vood, which ribs or laths are suitably located transversely to the co 'rugations or ribs projecting from the front face of the sounding-board.

In the accompanying drawing an embodiment of my present invention is illustrated by way of example. Fig. 1 shows the front side of the sounding-board, Fig. is a section on the line IIII in Fig. 1, and F 3 is a section on the line IIIIII in Fig. 1, Figs. 2 and 3 both showing the curvature or convexity of the board in an exaggerated way. Figs 4 and 5 show to a larger scale detail views of the sections of the board illustrated in Figs. 2 and 3, respectively.

As described in my copending patent application above referred to, the soundingboard is formed of a whole continuous metal plate 1 in which there are formed corrugations or bent-up folds or ribs 2 which have an approximately U-shaped or V-shaped cross section. The said ribs 2 preferably project above the front side of the soundingboard 1, to which side the bridge or bridges 5 over which the strings are stretched, are secured. lVhen attaching the board 1 to the fastening rim 3 by soldering or in any other suitable manner, each rib 2 is squeezed or PATENT orrics.

' 0113i, S v-VEDEN.

1922, Serial No. 590,229, and in Germany Z-Iovemocr 2, Zeal.

pressed together in suitable manner at its ends a at the edges of the sounding-board, so that the cross section of said ends l of the ribs becomes slightly narrower than that of the intermediate portions of the ribs, and in. this manner the edges of the sounding-board become contracted or shortened, so that the portion within said edges obtains certain oup-shape or convexity, and simultaneously, a certain tension wil be produced in the same.

According to the present invention there is provided on the side of the plate or sounding-board opposite to that from which the said corrugations or ribs project, ribs or laths 6, for: instance of wood. Said ribs or laths 6 are secured to the plate in suitable manner, for instance, as illustrated in Figs. l and 5, by means of screws 7 which pass through the plate on either side of the corgations or ribs 2 and are screwed into the abs 6, said screws thus being close to the 'ossing points of the corrugations 2 with the laths (3. Said laths 6 may also preferably be secured to the plate by means of a suitable cement or the like.

'lhe ribs or laths 6 will of course maintain the substantially plane portions of the plate or sounding-board between the corrugations 2 in proper position in alignment with one another, and said laths will thus eliminate the tendency of said portions to become displacedinore or less relatively to one another in a direction perpendicular to the plate owing to the tension in the same. The corrugations 2 and the laths 6 thus form toher what may be termed a latticework ior the approximately plane portions of the plate and thus a guide for the same, and siin ltaneously the sounding-board obtains an increased bearing power or spring. The

" divides the sounding-board into lattice-worn a large number of squares or panels, each panel forming, so to speak, a diaphragm which vibrates more freely than the surrounding ribs or laths, and thus more freely than the sounding-board as a whole. I have found that sounding-boards constructed in this manner become more sensitive and are therefore able to receive and to intensify a larger number of overtones than soundingboards constructed in the usual manner.

I claim:

1. A metal sounding-board for pianos pro vided with bent-up ribs having approximately V-shaped cross section and projecting above the front side of the sounding-board, each of said ribs being pressed together at its ends at the edges of the sounding-board, for the purpose of producing contractions of the edge portions of the sounding-board, laths being secured to the opposite side of the board substantiallycrosswise to said ribs.

2. A metal sounding-board for pianos pro vided with bent-up ribs having approximately V-shaped cross section and projecting above the front side of the sounding-board, each of said ribs being pressed together at its ends at the edges or the sounding-board, for the purpose of producing contractions of the edge portions 01' the sounding-board, laths being secured to the opposite side of the board, said laths extending transversely to the direction of the ribs on the front side of the board.

3. A metal sounding-board for pianos provided with bent-up ribs having approximately V-shaped'cross section and projecting above the front side of the sounding-board, each of said ribs being pressed together at its ends at the edges of the sounding-board, for tne purpose of producing contractions of the edge portions of the sounding-board, laths being secured to the opposite side of the board, said iaths extending transversely to the direct-ion of the ribs on the front side of the board and being rigidly secured to the sounding-board adjacent the crossing points of the ribs with the lathe.

FRIDOLF FRANKEL. 

